Me and NoOne have released Weapons Mod 4.0 for Blood. The mod basically adds new 22 weapons for Blood including restored weapons from Blood Alpha (it's still missing Spear Gun, maybe one day we will try to restore it). Go ahead and download it from here:

For example both Shadow Gun and Leech have different alternative fire or even the Book (replacement for Flare Gun) is using different animation for alternative fire. Normally they use the same animation for regular fire and alternative. And of course simpler changes like damage, ammo pickup, total ammo count, projectile replacement. Or another example, basically all melee weapons which are in WM are using Beast Claws code (Blood's 13th weapon) to get random fire animation, the only disadvantage is that the alternative fire is not working at all. Maybe in the next version we'll fix that, but it most likely requires even deeper hacking.